diff --git a/core/lib/Drupal/Core/Database/Schema.php b/core/lib/Drupal/Core/Database/Schema.php
index 7b884f7..5cb53b8 100644
--- a/core/lib/Drupal/Core/Database/Schema.php
+++ b/core/lib/Drupal/Core/Database/Schema.php
@@ -327,22 +327,35 @@ public function tableExists($table) {
    * Find all tables that are like the specified base table name.
    *
    * @param $table_expression
-   *   An SQL expression, for example "simpletest%" (without the quotes).
-   *   BEWARE: this is not prefixed, the caller should take care of that.
+   *   An SQL expression, for example "%" (without the quotes).
    *
    * @return
    *   Array, both the keys and the values are the matching tables.
    */
   public function findTables($table_expression) {
-    $condition = $this->buildTableNameCondition($table_expression, 'LIKE', FALSE);
+    $condition = $this->buildTableNameCondition($table_expression, 'LIKE', TRUE);
 
     $condition->compile($this->connection, $this);
+
+    $prefix_length = strlen($this->connection->tablePrefix());
+    $tables = array();
     // Normally, we would heartily discourage the use of string
     // concatenation for conditionals like this however, we
     // couldn't use db_select() here because it would prefix
     // information_schema.tables and the query would fail.
     // Don't use {} around information_schema.tables table.
-    return $this->connection->query("SELECT table_name FROM information_schema.tables WHERE " . (string) $condition, $condition->arguments())->fetchAllKeyed(0, 0);
+    foreach ($this->connection->query("SELECT table_name FROM information_schema.tables WHERE " . (string) $condition, $condition->arguments()) as $table) {
+      // Remove the prefix from the returned tables.
+      $unprefixed_table_name = substr($table->table_name, $prefix_length);
+      // The pattern can match a table which is the same as the prefix. That
+      // will become an empty string when we remove the prefix, which will
+      // probably surprise the caller, besides not being a prefixed table. So
+      // remove it.
+      if (!empty($unprefixed_table_name)) {
+        $tables[$unprefixed_table_name] = $unprefixed_table_name;
+      }
+    }
+    return $tables;
   }
 
   /**
diff --git a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
index 3eb5c84..5f871a4 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
@@ -1012,11 +1012,9 @@ protected function tearDown() {
     // entire parent site otherwise.
     if ($this->setupDatabasePrefix) {
       // Remove all prefixed tables.
-      $connection_info = Database::getConnectionInfo('default');
-      $tables = db_find_tables($connection_info['default']['prefix']['default'] . '%');
-      $prefix_length = strlen($connection_info['default']['prefix']['default']);
+      $tables = db_find_tables('%');
       foreach ($tables as $table) {
-        if (db_drop_table(substr($table, $prefix_length))) {
+        if (db_drop_table($table)) {
           unset($tables[$table]);
         }
       }
diff --git a/core/modules/simpletest/simpletest.module b/core/modules/simpletest/simpletest.module
index 5461cab..34549f7 100644
--- a/core/modules/simpletest/simpletest.module
+++ b/core/modules/simpletest/simpletest.module
@@ -591,7 +591,7 @@ function simpletest_clean_environment() {
  * tests.
  */
 function simpletest_clean_database() {
-  $tables = db_find_tables(Database::getConnection()->prefixTables('{simpletest}') . '%');
+  $tables = db_find_tables('%');
   $schema = drupal_get_schema_unprocessed('simpletest');
   $count = 0;
   foreach (array_diff_key($tables, $schema) as $table) {
diff --git a/core/modules/system/lib/Drupal/system/Tests/Module/ModuleTestBase.php b/core/modules/system/lib/Drupal/system/Tests/Module/ModuleTestBase.php
index aed76b3..d14ac2c 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Module/ModuleTestBase.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Module/ModuleTestBase.php
@@ -42,7 +42,7 @@ function setUp() {
    *   specified base table. Defaults to TRUE.
    */
   function assertTableCount($base_table, $count = TRUE) {
-    $tables = db_find_tables(Database::getConnection()->prefixTables('{' . $base_table . '}') . '%');
+    $tables = db_find_tables($base_table . '%');
 
     if ($count) {
       return $this->assertTrue($tables, format_string('Tables matching "@base_table" found.', array('@base_table' => $base_table)));